1. Field of the Invention
Priority is claimed on Japanese Patent Applications No. 2002-355464, filed Dec. 6, 2002, No. 2002-355437, filed Dec. 6, 2002, No. 2002-355453, filed Dec. 6, 2002, No. 2002-355397, filed Dec. 6, 2002, No. 2002-355418, filed Dec. 6, 2002, No. 2002-355379, filed Dec. 6, 2002, No. 2002-355485, filed Dec. 6, 2002, and No. 2002-355498, filed Dec. 6, 2002, the content of which is incorporated herein by reference.
The present invention relates to a VPN (Virtual Private Network). In particular, the present invention relates to a VPN which is called a layer 1 VPN or an OVPN in which various layer signals can be contained.
2. Description of Related Art
A VPN is a service in which users may feel as if they are using a private network while during using a private network. FIG. 1 is a view of a general structure for a conventional OVPN. According to such a conventional technique, as shown in FIG. 1, the OVPN is commonly formed by connecting optical exclusive lines 123 to 125 which are leased from a network provider between base points when the user form an OVPN between the base points. In such a case, the optical exclusive lines 123 to 125 are formed by optical cross connecting devices (hereinafter called OXCs) 10 to 12. Also, the OXCs 10 to 12 are formed from OVPN controlling terminals 13 to 15 to the controlling exclusive lines 1 to 6. When OVPN controlling terminals 13 to 15 are provided to the user, the user can control a part of function in the OXC 10 to 12 which belong to the network provider.
In such OVPN, there is a technique for forming an exclusive line which has a function for transmitting a layer 1 signal transparently such as SDH/SONET, OTN (Optical Transport Network). By transmitting various layer 1 signals (such as PDH, Ethernet (trademark registered), Gigabit Ethernet, Fiberchannel, SDH/SONET, or OTN) via a signal converter which contains the various layer 1 signals in a pass pay load of the SDH/SONET at an entrance of the network or in an optical channel (0 Ch) payload of the OTN and vial a signal converter which extracts and outputs the layer 1 signals which taken fro the pay load at an exit of the network so as to realize a function for transmitting a digital signal in the layer 1 transparently. However, it is not possible to handle a plurality of layer 1 signals by a signal converter except for a case of Gigabit Ethernet or Fiberchannel.
Therefore, the user of the OVPN must notify the layer 1 signals which the user is going to use to the provider of the OVPN in advance such that the desirable signal converter should by disposed in a terminating device in the OVPN for a case in which the OVPN is formed by the above signal converter. (See Document: “Proposal of Optical VPN service”, Misawa, Katayama, Okamoto, Yamanaka, The Society Conference of IEICE, SB-6-4)
Thus, it is possible to provide a function for transport the layer 1 signal transparently in a conventional OVPN. However, there is a problem in that it is difficult to exchange the signal converter and change a connection of the fibers when there is an urgent request that the OVPN user wants to change the contained layer 1 signal.